Nasa, Boeing Developing Space Launch System for Mars Rocket

In what could be billed as a step to build the most powerful rocket to take astronauts to Mars, Nasa has finalised a $2.8 billion contract with Houston-headquartered Boeing Space Exploration to develop its prestigious Space Launch System (SLS).

The six-and-a-half-year SLS contract runs through 2021 and calls for Boeing to deliver two SLS cores - including hydrogen and oxygen tanks - and avionics.

"Our teams have dedicated themselves to ensuring that the SLS - the largest ever - will be built safely, affordably and on time," Virginia Barnes, Boeing's Space Launch System vice president and program manager, said in a statement.

The rocket will carry the Orion spacecraft that can carry up to four astronauts beyond low-earth orbit on deep-space exploration missions, including the Red planet.

The rocket's core stage will get its power from four RS-25 engines - the former space shuttle main engines - built by Aerojet Rocketdyne of Canoga Park.

"Besides work on the rocket's core stage, the new SLS contract also authorises Boeing to begin studying a new SLS upper stage - which Nasa and Boeing call the Exploration Upper Stage," Nasa spokesperson Rachel Kraft said in a statement.

The rocket is scheduled for its initial test flight from Cape Canaveral in Florida in 2017.

The first mission will launch an empty Orion spacecraft.

The second mission in 2021 will launch Orion and a crew of up to four Nasa astronauts.